1. Field of the Invention
The present invention relates to a blind slat controller with braking function for rotating and locating blind slats at a predetermined light obstruction angle.
2. Description of the Related Art
A conventional blind slat controller is used to turn open blind slats for light to come into a room or close the blind slats to obstruct the light. The conventional blind slat controller generally includes a cord reel and two pull cords affixed to the cord reel. The pull cords can be pulled up and down to rotate the cord reel for driving and rotating a control shaft. The control shaft then controls the blind slats to rotate to a desired light obstruction angle.
U.S. Pat. Nos. 7,562,600m 6,761,204, 6,601,636, 6,561,254 and 5,636,677 disclose some typical blind slat controllers. The typical blind slat controller generally includes a cord reel and two pull cords wound on the cord reel. The pull cords can be pulled up and down to rotate the cord reel for driving and rotating a shaft rod. The shaft rod in turn drives a control shaft to control the blind slats to rotate to a desired light obstruction angle. The shaft rod is drivingly connected with the control shaft via a thread engagement transmission. There are gaps between the threads and the blind slat controller has no brake structure. Therefore, when the blind slats reach a predetermined light obstruction angle and a user stops pulling the pull cords to stop the cord reel from rotating, the weight of the blind slats will cause a downward pull force. Under the downward pull force, the control shaft is displaced in a reverse direction. In this case, there will be an error in light obstruction angle and the blind slats can be hardly located at the true light obstruction angle. Therefore, the blind equipped with the conventional blind slat controller has poorer light obstruction effect and cannot be accurately operated.
Moreover, the pull cords wound around the cord reel are generally directly suspended from the blind rail and positioned under the window. In this case, a child is likely to play the pull cords and get strangled. This is quite dangerous and leads to poor appearance.